The invention relates to a system for selectably equalizing an air pressure differential, relative to ambient, in the airspace between the pair of glass panes of double-glazed hermetically-sealed thermal insulating window units (hereinafter referred to as "hermetic window assemblies").
Hermetic window assemblies essentially consist of two or more glass panes spaced apart and provided with a hermetic seal about the entire perimeter of the panes. Such assemblies are useful for energy conservation purposes because the "dead air" trapped in the space between the glass panes serves as an effective thermal insulator to reduce the amount of heat transmitted through the window assembly. These window assemblies can, in the normal course of use, be subjected to a major change in ambient air pressure (for example, if a mobile home containing such windows is moved through a significant elevation gradient, or a window assembled at a sea level manufacturing site is used on the upper stories of a high-rise building). If the ambient air pressure is significantly decreased, the differential air pressure in the space between the panes will cause them to deflect outwardly, producing distortion and stress on the hermetic seal at the window's perimeter. On the other hand, if the window assembly were assembled at a high elevation, then transported to a lower elevation, the panes would deflect inwardly, similarly leading to stress on the perimeter's seal. Over time this stress could breach the structural integrity of the hermetic seal, thus allowing air and moisture to enter into the airspace, causing fogging and condensation on the interior surface of the glass panes and rendering the window assembly unusable. If the pressure differential of the ambient air pressure and the airspace between the panes should become extreme, the deflections of the panes may in time, particularly if there are repeated air pressure variations such as might occur in a mobile home transported to several locations at differing elevations, even be severe enough to fracture the panes.
Systems which automatically equalize the air pressure differential of the airspace between the glass panes of a hermetic window assembly and the ambient air are known to the art. McCurdy et al. U.S. Pat. No. 3,604,163 discloses a system for automatically equalizing the interior air pressure of a plurality of hermetic window units by ducting the interiors of the window units to a common manifold which is ported, in turn, to the ambient air. The manifold is equipped with a means for automatically releasing air when the manifold pressure exceeds the ambient air pressure, and yet permits air to enter into the manifold and thence the hermetic window units if the ambient air pressure exceeds the manifold air pressure.
Gelstharp U.S. Pat. No. 2,062,747 discloses another type of system for automatically equalizing the air pressure in the interior of a hermetic window assembly with the ambient air pressure. This system employs piping between the interiors of a plurality of hermetic double-glazed window assemblies together with a syphon which functions as a bellows and expands if the interior air pressure of the window assemblies is greater than ambient air pressure, and contracts if the latter is greater.
Such prior art systems are relatively complicated and costly because the equalization of the air pressure differential, between the ambient air and the interior of the window assemblies, is carried out automatically, and continuously, on a plurality of window units.
Thus, what is needed is an economical, easy to install and easy to operate system, for equalizing the air pressure differential of the airspace between the glass panes of an individual hermetic window assembly and the ambient air, which can be selectably actuated, as necessary, when this pressure differential becomes significant.